The hypothesis of this study is that the concentration of fluoride in oral interproximal fluids would increase more after using high-viscosity GIC as pit and fissure sealant, compared to Resin-Based sealants containing fluoride and RB sealants without fluoride content. To validate this hypothesis a randomized clinical trial was designed and performed in schoolchildren in order to evaluate fluoride release in inter-proximal fluid in vivo after the placement of three types of sealants: high-viscosity GIC, Resin-Based sealants containing fluoride and RB sealants without fluoride content.